If your DC attends school, how do you track your high achiever's academic progress?

I am feeling at a loss over the recent experience of realizing that the school is utterly uninterested in the fact that my DC's MAP test scores have not grown at all in one subject for an entire year (score over the 99 percentile for grade, but this will slowly slip over time if no growth takes place).

As I sit back and try to regroup, I find myself asking the question - how does a parent know whether their high achiever is actually making progress at their school? How do you track your DC's progress when they might be (repeatedly) hitting ceilings on grade-level assessments?